Asymmetric thiolcarbamates as herbicides



United States Patent 3,175,897 Patented Mar. 30, 1965 ice Thisapplication is a continuation-in-part of our application Serial No.633,529, filed January 11, 1957, now abandoned. This invention relatesto the use of certain novel compositions of matter as herbicides andmore particularly relates to the use of certainalkyl-N,N-dialkylthiolcarbamates wherein the two N-bonded alkyl radicalsare different. Thus, the compounds of the present invention differ fromthe compounds of our Patent 2,913,327 in having asymmetric substituentson the nitrogen atom.

It has been found that the compounds having asymmetric substituents havea much higher safety factor on certain important crops than do thecorresponding symmetric compounds of Patent 2,913,327. On crops such assugar beets, tomatoes, strawberries, spinach and soy beans, thesymmetric compounds, if used in sufiicient quantity to be effectiveherbicides, cause a severe reduction in the desired crop, so that theuse of the symmetric compounds on such crops is economically unfeasible.The most widely used of the compounds claimed in 2,913,327, namelyethyl-di-n-propylthiolcarbamate, causes a severe reduction in yield ofsugar beets, while the compounds of the present invention not only actas effective herbicides but actually increase the yield. Further, theasymmetric compounds of the present invention leave no residue on thedesired crop, and the effects disappear from the soil rapidly so thatthere is no carryover to a subsequent crop.

The compounds of the present invention have the formula Example I About10 g. (0.08 mol) of ethyl chlorothiolformate was dissolved in 125 cc. ofethyl ether and the solution was cooled in an ice bath to 5 C. To thismixture was then slowly added 16.7 g. (0.165 mol) ofN-ethyl-nbutylamine. The precipitated amine hydrochloride was thenremoved by filtration and the filter cake was washed with a littleether. The washings were combined with the original filtrate and theother solution of product was concentrated on a steam bath. The residualliquid was transferred to a 50 cc. round-bottom flask and the solventwas completely removed at 25 C. and 25 mm. Hg pressure by means of aRinco rotating film evaporator. There was obtained 12.0 g. (79% yield)of ethyl ethyl-nbutylthiolcarbamate, N 1.4758.

Example II When the general procedure of Example I was repeated exceptthat 14.9 g. (0.148 mol) of N-ethyl-n-butylamine and 10 g. (0.072 mol)of n-propyl chlorothiolformate were employed, there was obtained 14.0 g.(96% yield) of n-propyl ethyl-n-butylthiolcarbamate, N9 1.4742.

Example III When the general procedure of Example I was repeated exceptthat 21 g. (0.165 mol) of N-ethyl cyclohexylamine and 10 g. (0.080 mol)of ethyl chlorothiolforrnate were employed, there was obtained 15.9 g.(91.8% yield) of ethyl ethylcyclohexylthiolcarbamate, Nj 1.5069.

Example 1V When the general procedure of Example I was repeated exceptthat 1'8.8 g. (0.148 mol) of N-ethyl cyclohexyL amine and 10 g. (0.072mol) of n-propyl chlorothiolformate were employed, there was obtained15.4 g. (93.5% yield) of n-propyl ethylcyclohexylthiolcarbamate, N1.5031.

The compounds of the present invention are ordinarily applied aspro-plant treatments to the soil. Although the compounds can be appliedin their pure form, it is ordinarily more convenient to formulate thecompounds in the form of an emulsifiable concentrate and apply anaqueous emulsion made therefrom to secure uniform application. Thecompounds can also be formulated as solutions, dusts, or wettablepowders. The compounds are normally mixed into about the top two orthree inches of soil, using harrows, disks or similar agriculturaltools. Planting can immediately follow application and, in manyinstances, the compounds can be applied and the seeds planted using asingle tool. For economy, the compound is often not applied to an entirefield but is applied as a narrow band straddling the seeded area,leaving the space between bands to be treated by the usual mechanicalweed control methods. The rate of application of the active compounds isfrom about 2 to 20 pounds per acre and in most instances a rate ofapplication of from about 4 to about 8 pounds per acre will. giveeffective weed control without damage to the desired crop. The treatmentrates per acre are based on the actual area treated, so that if thecompound is applied in narrow bands, the rate of application per fieldacre will be much lower than that indicated.

The following example shows the effectiveness and safety of twocompounds of the present invention as compared with the compound ethyldi-n-propylthiolcarbamate, the best compound from Patent 2,913,327. Thiscompound has the code designation R4608 and is sold under the registeredtrademark Eptam. In this series of tests, fields were planted to sugarbeets near Freeport, California. After applying the compound to the soilas an emulsion of the compound. in water, the compound was incorporatedin the soil by going over the soil with a spike-tooth harrow and a ringroller twice, the treatments being at right angles to each other. Therate of application was 2 and 4 pounds per acre. The soil involved washeavily infested with water grass and lambsquarters. At 2 pounds peracre, none of the compounds gave more than fair control oflambs-quarters, while at 4 pounds per acre, all of the compounds gaveexcellent control of both water grass and lambs-quarters. How- 3 ever,at an application rate or" 4 pounds per acre, the growth of sugar beetswas only 70% of normal with compound R4608, while it was 100% normalwith the In other tests, compound R4063 was applied at 4 pounds per acreon spinach and germination and growth were completely normal, whileweedcontrol was excelcompounds R-2060 and R-2061. lent. Compound R-2064gave excellent weed control In the same series of tests, tests were madeto see 5 on soy beans at 3 pounds per acre, with 100% germinawhetherthere was a chemical residue in the soil which tion and 90% growth ofthe desired crop. At these Would interfere with subsequent crops.Samples of the rates, R-1608 gave severe reduction in the desired crop.soil were taken 12 weeks after application and planted We claim: tooats. .In the case of compound Rl608 at 4- pounds 1. The method ofpreventing the growth of Weeds in per acre, germination was severelyreduced, while with the presence of sugar beets, tomatoes, strawberries,compounds R-2060 and R2061, at the same rate, germispinach and soy beanscomprising applying to the soil nation was completely normal. aphytotoxic amount of a compound having the formula In the above seriesof tests, five random samples were 0 obtained, each from the plottreated with R2061 and ll from a check plot which had not received anychemical 15 treatment. The plot treated with R2061 had been treated R3at the rate of 4 pounds per acre. On the check plot, the Whcrehl 1 isShlecied from the group Consisting of ethyl yield of beets was 9.57 tonsper acre, while on the treated and -P PYL Whfifehl 2 is ethyl andwherein 3 is plot the yield was 10.95 tons per acre, and the sucroseSelected from the g p Consisting of y and y content of the treated beetswas higher, so that the overheXyL all yield on the check plot was only2,603.9 pounds of method of Prevhhhhg lhs growth of Wehds in sugar peracre, while on the treated plot the yield was the Presfime Sugar hfieis,tomatoes, Strawberries, 3,1211 pounds f sugar per acre spinach and soybeans comprising applying to the soil Si il t t m d on tomatoes, A an lia phytotoxic amount of ethyl ethyl-n-butylthiolcarbamate. tion rate of 6pounds per acre, compound R-2061 gave The method of PYeVehhhg the growthof Wefids in a normal yield of tomatoes and gave excellent control ofthe Pffisehch of Sugar befits, tomatoes, Strawberries, red root pigweed, water grass, purslane and lambs- Spinach and Y beans Comprising ppy U16 Soil quarters. In the same field, application rates of comaPhYYOYOXiC amount P PY y y pound R-l608 killed all of the tomato plantsat applicalhamateti rates f 3 d 6 pounds per acre, 39 4. The method ofpreventing the growth of weeds in In another series of tests the seedsof various plants thh Presence of Sugar beets, tomatoes, SEW/berries,were planted in 3" diameter paper cans in Santa Cruz spihdhh and Yh-gahs comprising pp y to Soil loam. The cans were watered and an amountof each a PhYtOlOXiC alhhhht of athyl ethy'lcyclohhXyhhiolcompound wasapplied as an acetone solution to each Cafhamathcan which wouldcorrespond to a rate of application of The Ihhthcd of Preventing the g0f ds in 3 pounds per acre of h actual compound under test the presenceof sugar beets, tomatoes, strawberries, Similar controls were plantedand all of the cans were spinach beans minimising applying the SOilmaintained in a greenhouse, watered as needed and the a Phytotoxlcamount of I1"Pmpyl fithylcyclohexyhhiolgermination and growth of thetreated cans were compared 40 Cuba-mate" with the controls. Germinationwas reported on a scale of 0-100 and growth on a scale of 0-10; and 10Refemnces Clted m the file of thls pawn, represent, respectively, nodeviation from the control. UNITED STATES PATENTS The following datawere obtained. 2,913,327 Tilles et al. Nov. 17, 1959 Red Oats PigweedSudan Grass Nut Grass Yellow Quack Water Foxtail Grass Grass CompoundGe. Gr. Ge. Gr. Ge. Gr. Ge Gr. Ge. Gr. Ge. Gr. Ge. Gr.

1. THE METHOD OF PREVENTING THE GROWTH OF WEEDS IN HE PRESENCE OF SUGARBEETS, TOMATOES, STRAWBERRIES, PINACH AND SOY BEANS COMPRISING APPLYINGTO THE SOIL A PHYTOTOXIC AMOUNT OF A COMPOUND HAVING THE FORMULA